A ship A is moving West wards a speed of 10 kmh−1 and a ship B 100 km South of A, is moving North wards with a speed of 10 kmh−1 .The time after which the distance between them becomes shortest, is :
5h
VBA=10√2km, ∝=45∘
AN = minimum distance between the two
= d cos ∝
Time taken to reach at N = d cos αVBA= 100×1√210√2=5 h